1. Technical Field
The present disclosure relates to a hydraulic stopper of a shock absorber, which restricts an excessive rise of a piston rod and, more particularly, to a hydraulic stopper of a shock absorber, which uses oil pressure to restrict rise of a piston rod in a rebound stroke.
2. Description of the Related Art
In general, a vehicle is provided with a suspension system for enhancing driving comfort by buffering impact or vibration transmitted from a road to an axle during driving. One component constituting the suspension system is a shock absorber.
FIG. 1 is a sectional view of a conventional shock absorber. Referring to FIG. 1, the shock-absorber 10 is disposed between an axle and a chassis, and includes a cylinder 12 and a piston rod 14 reciprocating in the cylinder 12. The cylinder 12 may be a single tube, or may be a dual tube that includes an inner tube 12a and an outer tube 12b as in an embodiment of the present disclosure.
Further, the cylinder 12 is provided at an upper portion thereof with a rod guide 16 that maintains a space between the inner tube 12a and the outer tube 12b and guides movement of the piston rod 14. Further, the cylinder 12 is filled with a buffering medium, such as gas, oil or the like, which is moved by a piston valve secured to one end of the piston rod 14 to generate a damping force.
In such a shock absorber 10, a stopper 20 is mounted on an outer circumference of the piston rod 14. The stopper 20 restricts an upward rise of the piston rod 14 upon excessive rebound, so that the piston valve can be prevented from damage and has improved roll characteristics when turning.
The stopper 20 may be attached to the piston rod 14 by welding or assembly. The stopper 20 includes a stopper bracket 22 secured to the piston rod 14, and a buffering part 24 provided to an upper portion of the stopper bracket 22. Here, the buffering part 24 is made of an elastic material and is deformed to absorb shock when coming into contact with a lower end of the rod guide 16.
With such a general configuration, there is a limitation in that the stopper 20 of the shock absorber 10 cannot sufficiently absorb shock when the piston rod 14 moves excessively upward. Accordingly, if an iterative and high load is repeatedly applied to the shock absorber, the buffering part 24 of the stopper 20 can be damaged, thereby causing product failure, noise and deterioration of driving comfort
To overcome the limitations of the general stopper 20, a hydraulic stopper has been recently developed and used, which employs oil pressure to generate a buffering effect.
Since the buffering effect of the hydraulic stopper is controlled depending on the length of the rod guide, however, the rod guide and the shock-absorber must become longer in order to provide a higher buffering effect, thereby causing an increase in manufacturing cost while deteriorating yield. Further, a conventional hydraulic stopper employs a stop ring for controlling the buffering effect. In addition, not only does the hydraulic stopper necessitate a separate process for formation of orifices in the stop ring, but also has a problem in that the orifices formed in the stop ring are not uniformly distributed, deteriorating quality and reliability of the shock absorber.